Coatings World - August 2016

Lisa Spagnola, Jeffrey Klang, Manjuli Gupta, Sartomer, Americas;

Xavier Drujon, Sartomer, Europe

Soft-touch or soft-feel coatings are mployed to create a variety of hap- tic effects on plastic, paper and metal substrates. Haptic effects can improve a consumer’s perceived value of the product, and influence them to buy the product over other similar products. In fact a recent study by California Polytechnic State University showed not only did customers prefer cosmetics packaged in a container with a soft touch coating versus a traditional coating, they were willing to pay a 5% price premium.1 Thus it is no wonder interest in soft-touch coatings has increased in recent years. While the study by California Polytechnic State University focused on cosmetic packaging, soft-touch coatings span a variety of markets including automotive interiors, small electronics, and appliances.

With the broad range of markets
comes the need for a broad range of feel
types. In general, a feel type is described
in terms of things known to be soft, such
as rubber, velvet, peach skin, rose petals,
silk, leather, suede, etc. Not only are these
terms highly subjective, the perceived feel
varies from person to person. A coating
that one observer might describe as vel-
vety, another may find silky. Studies have
shown that factors such as age2 and sex3
affect how feel is perceived. In a previous
lab study we chose observers of various
age, sex, and training. 4 Although most
could recognize a soft coating, their per-
ception of which was the most pleasing
varied widely. While we found atomic-
force microscopy (AFM) measurements
can distinguish between feel types when
the coating chemistry was different, 4
additional testing showed that as the
chemistry became more similar, the re-
lationship between adhesion force and
feel no longer held. In addition, AFM
cannot distinguish the quality of the feel.
Thus, for our subsequent studies we used
trained observers to judge the quality and
type of the feel effects.

Since consumer products are exposed to repeated wear and contaminants throughout their life cycle, soft feel coatings must also be durable. Balancing soft feel with wear resistance is an additional challenge. Wear resistance for soft feel coatings is typically created by crosslinking multifunctional isocyanates with polyols. This process creates hard regions from the isocyanates distributed in softer regions created by the polyols, as can be seen in the idealized structure in Figure

1. While these two-part systems have excellent feel properties, two-part urethane coatings have disadvantages such as pot life limitations, long cure times, and hazards of isocyanate handling. To address these issues as well as to improve durability, formulators and product designers look increasingly toward UV-cured soft-feel coatings.

In a previous study, inspired by two-part
isocyanate systems, we demonstrated our
ability to create a UV-curable soft-touch
coating with good feel and improved mar,
abrasion, stain, and chemical resistance
compared to conventional two-part ure-
thane coatings. 4 The system created had a
silky feel. Achieving soft-touch coatings of
various feel types is necessary to fit the re-
quirements of a wide range of applications
and products. This article details the de-
velopment of a range of custom designed
UV-curable soft touch products that have
tailorable feel and improved properties
over two-part urethane coatings.
New Advances in